CPTOZZY

I have lost 4 Planes in 3 weeks, 3 of the four I I have no doubt were caused by Transmitter failure The were fully charged & gassed and lost control within a short distance of where I was standing. my 4th was a bit low on both Battery and Fuel, which may have contributed.

On our Airfield we have a A large Radio Tower at one end and a Jail at the other end. Guys from my club believe the Cell phone Jammers coming form the Jail may have caused my problems (and some others).

I previously sent in my receivers to Horizon who said they were ok, I just sent in my DX8. If it doesn't fix this problem I'm switching to Futaba


Any Advice - Similar Stories out there?

CPT Ozzy

AndyKunz

Cell phones are on a very different set of frequencies, far away from 2.4gHz. You could have a phone call on your cell phone while you're flying and it would cause exactly 0 problems.

How did the transmitter fail that you are sure it was the transmitter?

What receivers were you using? Was a receiver previously involved in a crash?

How were your powering the receivers? Be very specific with actual products used.

What size are the airplanes you are using?

What type of airplanes?

What is your flying style?

What servos did you have in the aircraft? Have you ever measured the current requirements? How do you test the linkage resistance?

I have heard similar stories, yet when we do the research it almost always turns out that the aircraft was not well-assembled (ie, high resistance in linkages), inappropriate servos, inappropriate receiver power system, wrong type of receiver for the application (ie, a small park flyer rx in a 50cc 3D plane), etc. There have been precious few actual failures of transmitters. The assumption that it's NOT the transmitter is by far the correct assumption.

If you answer those questions above, perhaps I can help you prevent failure in your future radio choice.

Andy

CPTOZZY

I use spectrum receivers. On the 4 Failures 3 of the receivers were Spektrum 6210's, the other was n AR 600. I had failures with 2 Glo Fuel planes(One 40 size and one 60 size) using 6 volt battery pack, and two failures were with electrics, one of the electrics was the E-flite Carbon-Z Yak 54, the other electric used a Plush 60 ESC. on 3 of the 4 crashes I lost control very close to my position (about 20 yards). A week after I lost my last one a buddy at the airfield lost one of his nitro planes in the same Airspace "box" that I lost 3 of them (He was using a Spektrum dx 7).

As for Linkage resistance Everything was smooth No servo Hum or Chattering

All these planes had been flown multiple times with no problem, and I had been using this transmitter for over a year with no problems, then I Lost one Plane, the following week I lost two, and the next time I flew I lost the fourth

after the first crash I sent one receiver in to Horizon Hobby, and they checked it out and said it was fine. I just sent in the DX8 to have it checked out. Some guys at my field say that there have been similar problems with the DX8's. If It Checks out I'll give it another shot (I Really do like the transmitter) , but If I lose another I'm going to switch to Futaba

AndyKunz

Thanks for the info. It's not quite what I was looking for. Instead of an inventory of components, I was looking for something like this:

"AR6210, (6) HS-81 servos, 5-cell NiMH 600mAh pack. I fly extreme 3D. Servo current never exceeded XXXmA on any servo (Hum or chattering means zilch, sorry)."

or

"Pure stock Carbon Z Yak, even the stock prop."

By failure it would help to know exactly what happened. Like, "I was setting up for landing after my third 12-minute flight and it snapped off to the left and crashed."

How were your range checks going? When you had your first problem, did you range check afterwards? Do you use telemetry? (Man, is that a life-saver! If anybody who reads this isn't, try it and find out!)

I don't mean to scare you, but if you don't measure things like servo currents and battery consumption you are setting yourself up for failure with any other brand too. Sometimes the problem isn't the plane, isn't the transmitter, or the receiver. Sometimes it's just that things needed a little TLC and maintenance - hinges get loose, linkages get sloppy, and servos wear out. Sometimes the placement of the electronics in the model is the culprit.

One of my friends from work is a big-name jet guy. He would travel around to clubs in the area and go to their meetings to give instructional presentations. Anyway, he was telling me about the time he went to a club and had told the guys to bring along a plane so he could help them go through it for proper operation. One of them had an aerobatic model that "only" drew about 3A or so with the plane sitting on the ground. It was supposedly set up properly. He went through the whole plane with them watching and in the course of half an hour had the current draw down to about 1/4 of that simply by fixing linkages and hinges. Mind you, this plane belonged to somebody who "knew what he was doing" - one of the "pro class" kind of guys.

I hope you do get it sorted out, and I don't blame you for feeling like changing brands. Before you jump ship, please check out the plane and get some real numbers for things. KNOW what is happening in your plane. For me this is where telemetry showed me how close I had been skating to the edge. I never realized how bad my planes were. It was awful because I spent a ton of time and some money reviewing each plane to fix it up or get better BEC/ESC, etc. As a result I haven't crashed due to an equipment failure since before we shipped the first DX8's. And just because a plane is box-stock doesn't mean that you might not learn something from telemetry. Do it anyway.

Andy

chuckk2

A remote possibility has to do with the TX battery leads. I have one Futaba TX battery that had an intermittent wire to connector pin crimp.
Really puzzling problems like yours may show up if you have any way to temperature cycle the TX over a reasonable range.Things like cold/poor solder joints as an example. another one is slightly flexing various circuit boards inside the TX.
Cell Phone jammers are basically illegal, and thus may have all kinds of RF out at unexpected frequencies.
(Something about interfering with legal communication devices.)

That aside, the problems I've had chased down to insufficient current capability from the RX power source.
(ESC's with an internal 2A SBC, or NMIH 2000-2500mah packs that had a significant voltage drop under
high momentary load.) Fortunately, in my case, circumstances were such that recovery was made with little or no damage.
(Depending on the RX, it may take up to 3 separate bind sequences to get the default and fail safe settings to completely "take".) One of the almost crashes due to control loss was interesting, in that control returned for some channels, and not others. Never did figure out why that happened.

Len Todd

4 planes down, off one transmitter: I'd be looking at the transmitter, too, I would send it in and have it tested. Ask the Tech to give you a call when he starts. Tell him what you think is going on and let him go to work! He'll call you back. As Andy said, it is a low probability of the DX8 being the problem. But, they occasionally have a failure. At least this way you can rule it out.

I just sent one of my DX8's back in and they "cooked it" for a couple hours and it still was transmitting at 10dB. So, ... now I know to look elsewhere for the source of that unexpected "hold" that I saw. Maybe I need to stop flying past the opposite end of our 3800' runway.

Andy is right about telemetry. It can save your plane. I use it in my Giants. It helps me gauge how far out I can fly as well as helps me monitor battery voltages, etc.

On a "known not to be pilot error" crash, my first thought would to get a look at the flight log data, if possible. I would also be taking a look at the Receiver Voltage, if the battery was still connected. You can do this all on the DX8 telemetry, long before you walk out with the garbage bags. However, you need to get Flight log data before you pull the battery or it gets pulled for you. They even have a pocket data reader. I have used mine in the smaller planes, many times just to check antenna placements.

With telemetry, you can get an alarms on Frame losses, which occur before Holds. If you don't see a Hold on a crashed plane's flight log data, you know it was not the RF signal. With telemetry and alarms set, you would get an alarm before an RF Failure related crash. You can also get alarms on low Rxer voltages that occur when current spikes take place (e.g. messed up servo). We are told that most planes crash because of inadequate battery power. What were the pre-flight voltages on your batteries? Maybe your charger died? What type of batteries are you using? Some types of batteries false peak. How old were they? Was each crashed plane re-using the same batteries? I would load test the involved batteries and compare the results to fresh packs.

Last Question: What does a range check on the suspected DX8 tell you? We had a Futaba system go down in a Giant about two hundred yards out. Later, the pilot replaced the plane and used the same Rxer, We stopped him and did a range check. During the range check the tail feathers dropped about 70' away. I think he junked that Rxer. Points being: loss of signal happens to all brands and your first indication of a potential problem with the transmitter and/or receiver is the failed range check.

By the way, the 2.4 Ghz band is an odd-multiple of the cell-phone bands. Third order harmonics are possible, but not likely. We use the cell phones at the field all the time. Also, the DSMX protocol looks for clear frequencies. (Why don't they just do a full shakedown every now & then and increase visitor security to rid the jail of phones? Using jamming seems a bit extreme and not very healthy for the guards.) Also, I am not sure if the FCC even allows jamming by a local facility. ?

AndyKunz

No it doesn't, but it doesn't need to because it's not there very long. Just a blip and if it's missed, not big deal since there's another one coming in a few milliseconds on a different frequency. DSM2 would look for open channels; DSMX does not.

Andy

JohnB96041

Andy: Ran into an issue that has me concerned. I have the DX8 with the AR8000 receiver. While setting up rates on each of the switches (0,1,2) for elevator, aileron, and rudder, I have noticed that the aileron tripple rates will cause the ailerons to drift/move when moving the aileron switch from low, to medium, to high. This does not happen with the tripple rate settings on the elevator or rudder. The movement of the ailerons is enough to cause the aircraft to roll to the right when moving from low rates to medium rates and do a very fast roll with moving from medium rates to high rates. Any suggestions as to how to correct this issue? Thanks.

Len Todd

Suggestion: Put a servo tester between the servo and Rxer. Read the resolution. If the resolution reading is moving, then try another RXer. If the Resolution is still moving, then send in the Txer. If the resolution is not moving in either case, try a spare servo. Sometimes the servo pots get corroded or worn out. I had that happen once.

JohnB96041

Both the right and left aileron servos are new. They both move when changing the rate switch for aileron. Right aileron is on port Ail, left aileron is on Aux1.
I have other models setup the same way and when I change the TX to a different airplane the rate switch does not cause any of the servos to move, just changes the rate. What if I reset this particular model and re-program it. Do you think this will correct the issue?

AndyKunz

My guess - you have Flight Mode vs. Common trim.

Andy

JohnB96041

OK.....dumb question? I am assuming I should be in Common Trim. How do I check this Flight Mode vs Common trim issue?

Len Todd

Actually, I put all three surfaces on the Fight Mode switch and change all three at once. Works a lot better for me.

With the Txer working correctly on the other plane, it sounds like the Rxer may be your problem. Measuring the resolution with a servo tester on the output would verify that. But, we are dealing with two channels drifting. Of course the Aux 1 is only looking at the Aile. If Aile drifts, probably the Aux 1 just follow. Back to the Rxer.

BTW: Just because the servo is new does not mean they are good. But with two servos drifting, your still back to the Rxer.

I would be looking at the Rxer output with a servo tester. Then, I would try a Rebind and try it again. If there is still a problem, then I would try starting a new model in the transmitter, rebind and try it. If all that fails to correct it, then I would put in a spare Rxer on the Aile and see what happens. Probably might do that first anyway.

AndyKunz

Trim Setup screen shows that.

Andy

JohnB96041

Andy: Problem solved. I did a re-calibrate of the left, right, and knob on the TX. Problem solved. After a rebind, the ailerons DO NOT move when changing from low to medium to high rates. Dead centered.

AndyKunz

Good to hear that, John!

Andy

JohnB96041

Now the big question. What could have caused this to get out of calibration? I did upgrade the TX from the original battery to the LiPo battery from Horizon Hobby and upgraded the receiver battery to a Life battery with regulator. Could that have caused the TX to get the control sticks out of calibration or is this something that should be re-done every so often?

AndyKunz

The batteries had no action. The battery voltage is immediately dropped down to a constant level for the entire radio to use. The only thing that ever sees the full battery voltage is the power switch and the voltage regulator.

I have a DX8 which I haven't recalibrated in several years. It works just fine. My DX18 likewise has been over a year.

The calibration would have no interaction with flight modes unless there were a mix or trim associated with one of the other inputs that would cause it, or if you had different rates in the different modes. In that case it would be caused by the fact that the sticks weren't saying center when they were physically there (which is what calibration does for them), and if you had different rates then it would appear because the offset from 0 would be amplified at high rates.

Calibration can change slightly due to mechanical causes such as one spring not having the same tension it had earlier, or for wear in the mechanics. That wear could be usage or temperature induced, or affected by dirt.

Now that you have it calibrated, watch the centered value on the sticks. It should be in the range -1 to 1, typically 0. "Twang" the sticks slightly to allow the springs to center them, rather than trying to center them yourself. Do it several times. Try it again mid-season, and again late-season and see if they change. It's possible but totally normal.

Remember after calibrating the sticks that you may need to tweak the trims in flight again.

Andy

JohnB96041

Thanks Andy. Great information. I will keep an eye on it from now on (hope the old brain remembers all this info).

Len Todd

So,... How do you calibrate the sicks? The manual does not say a thing about that.

JohnB96041

Page 40-41 in the manual......

JohnB96041

If I remember correctly, it is under the system settings menu. Keep going down via "next" until you see it.

Len Todd

Thanks. I'll go back down and take another look in "the book."

On Edit: Yep calibration is there. But,... if this drifting effect was not seen on the other planes, how did a recal fix this? If it was the stick calibration, seems like you should have seen that same drifting effect on the other planes. The other thing you did was rebind. Anyway, ... you got 'er fixed. Good to know about calibration, too. Learn somethin' new every day!

JohnB96041

Another question about the DX8. What effect does the temp have on the DX8 transmitter? I have noticed a really funny sounding warning (nothing on the screen) when I turn on my TX. Temp is in the low 20's and high teens. Everything works correctly once the tx boots up but it makes a really weard sound. The only warning I have set is a high throttle warning. The throttle warning activates with the stick at the 20% throttle setting. The funny sound happens as the system is turned on and boot process happens. Any ideas???

AndyKunz

It's normal. As the radio boots it's reporting changes to the model from when you shut it down. If you've moved switches, etc. it will make appropriate sounds for some of those items.

Andy